Device architecture

ABSTRACT

A device for contactless communication with a terminal, the device comprising: an antenna for receiving a wireless signal emitted by the terminal; an embedded chip configured to generate data for communication to the terminal to perform a first function associated with the device; and a module separate from the chip configured to perform processes as part of a second function associated with the device, the module being connected to the antenna and comprising a power-harvesting unit configured to harvest power from the received wireless signal to power at least the module.

FIELD

This invention relates to an architecture of a multifunction device. Inparticular, certain aspects relate to the architecture of a device thatcan operate in a contactless mode of operation.

BACKGROUND

A smart card may refer to a device that includes an embedded integratedcircuit chip and internal memory. That internal memory may be located onthe integrated circuit chip, or be a separate chip embedded within thecard. A smart card may be a contact card; a contactless card, or may becapable of operating as a contact and a contactless card. Smart cardsexist in a wide variety of form factors, including plastic cards, keyfobs, watches, wearables, electronic passports and USB-based tokens andsubscriber identification modules (SIMs) used in mobile phones.

A contact card communicates with a terminal (e.g., a card reader) byphysically connecting to the terminal. For example, a contact card maycomprise one or more contact pads that provide electrical connectivityto a terminal when the card and terminal are brought into suitablephysical contact (e.g. by inserting the card into a slot within theterminal).

A contactless card communicates with a terminal without direct physicalcontact. Typically, a contactless card communicates with a terminal viaradio waves. The contactless card may include an antenna to receive anelectromagnetic signal, such as an RF signal, emitted from a terminal.Likewise, data from the card can be communicated back to the terminal bymeans of the card's antenna.

Some contactless cards are ‘passive’. A passive card powers the embeddedchip from energy harvested from the signal emitted by the terminal. Oneway to harvest energy from the emitted signal is to arrange the antennaas a coil that induces a voltage across its terminals by means ofinduction when receiving the emitted signal. Smart card technology isbeing implemented within a variety of devices used to performincreasingly varied functions, for example to perform payments, grant auser physical access to a region of an environment, to store personalidentification information of the user; identify or authenticate a useretc. In some cases, it may be desirable for a device to be capable ofperforming multiple different functions.

There are several difficulties faced when trying to implement multiplefunctionalities into a device using smart card technology, particularlywhen a device designed to perform a ‘base’ or primary function isadapted to perform additional functions. One problem is that industrystandards governing smart card technology were originally designed forpayment/authentication cards. Existing infrastructure has therefore beendesigned in compliance with these standards that is suitable forpowering this primary function of facilitating payments or transactions,which may place constraints on the power that can be consumed by anyadditional functionality placed onto the card. This problem may becompounded by the fact the additional functions may consume more powerand/or require power for a longer period of time than the primaryfunction of the card. A further problem is that for cards operating in acontactless mode, the power drawn by the additional functionality mayaffect the load modulation of the signal emitted by the terminal, whichmay appear as extra noise to the terminal.

SUMMARY

According to the present invention there is provided a device forcontactless communication with a terminal, the device comprising:

-   -   an antenna for receiving a wireless signal emitted by the        terminal;    -   an embedded chip configured to generate data for communication        to the terminal to perform a first function associated with the        device; and    -   a module separate from the chip configured to perform processes        as part of a second function associated with the device, the        module being connected to the antenna and comprising a        power-harvesting unit configured to harvest power from the        received wireless signal to power at least the module.

The module may be connected by a link to the chip, the module comprisinga power management unit configured to control transmission of harvestedpower to power the chip.

The module may be configured to manage the transmission and reception ofmessages with the reader containing data generated by the chip.

The chip may be connected to the antenna and comprise a power-harvestingunit configured to harvest power from the received wireless signal topower the chip.

The module may be configured to harvest power from the received wirelesssignal independently of the chip.

The module and chip may each comprise a dedicated microcontroller unit(MCU).

The device may be configured so that only the chip is arranged to managetransmission and reception of messages with the terminal.

The device may be configured so that only the chip is adapted tocommunicate messages with the terminal via the antenna.

The chip may comprise a modem configured to extract data from thereceived wireless signal emitted from the terminal.

The modem may further be configured to modulate data generated by thechip onto the signal emitted by the terminal to communicate the data tothe terminal.

The device may be for contact and contactless communication with theterminal, and may further comprise:

at least one contact element connected to the embedded chip and themodule and arranged to supply power to the embedded chip and the modulefrom the terminal when the device is in contact communication with theterminal.

The module may further comprise noise mitigation circuitry configured touse power harvested from the received wireless signal as the device isbrought into range of the terminal to store charge.

The noise mitigation circuitry may be configured to supply currentdemanded from one or more components of the module to inhibit currentbeing drawn from the antenna during operation of those components.

The noise mitigation circuitry may be located within the powerharvesting unit.

The noise mitigation circuitry may comprise one or more chargingelements for storing charge, the charging elements being arranged todischarge to supply demanded current.

The noise mitigation circuitry may comprise a rectifier circuit coupledto the antenna and configured to output a rectified voltage to charge afirst charging element.

The noise mitigation circuitry may further comprise supply regulationcircuitry configured to output a regulated voltage to charge a secondcharging element.

The noise mitigation circuit may further comprise a control blockconfigured to control the amount of current supplied to the one or morecomponents from the charging elements in dependence on deviations ofdemanded current from those components.

The noise mitigation circuitry may comprise a first voltage regulatorcoupled to the rectifier circuit and a first component of the module,and a second voltage regulator coupled to the rectifier circuit and asecond component of the module, the first voltage regulator beingconfigured to output a different regulated voltage level than the secondvoltage regulator.

The first component of the module may be an ASIC configured to control asensor forming part of the module, and the second component of themodule may be a microcontroller unit.

The first voltage regulator may be configured to output a higherregulated voltage than the second voltage regulator.

The first voltage regulator may be a low-dropout regulator, and thesecond voltage regulator may be a switch-mode-power supply.

The noise mitigation circuitry may be located locally at a component ofthe module.

The chip may be a secure element. The chip may be a first integratedcircuit chip, and the module may be implemented on a second integratedcircuit chip.

The module may be a biometric sensor module.

The device may be configured to communicate with the terminal inaccordance with the ISO14443 and/or the ISO7816 standard.

The first function may be one of: ID verification; physical accesscontrol; a financial transaction; personal information retrieval; healthrecord retrieval.

The second function may be a biometric authentication of a user.

The device may be a contactless card and the terminal may be a point ofsale terminal.

There is also provided a device for communicating with a terminal in acontact or contactless mode of operation, the device comprising:

-   -   an antenna for receiving a wireless signal emitted by a        terminal;    -   an embedded chip configured to generate data for communication        to the terminal to perform a first function associated with the        device;    -   a biometric sensor module separate from the chip and configured        to perform processes forming part of a biometric sensing of a        user feature, the module being connected to the antenna and        comprising a power-harvesting unit configured to harvest power        from the received wireless signal to power one or more internal        components of the module when the device operates in the        contactless mode of operation; and    -   one or more contact elements configured to supply power to the        biometric sensor module from a terminal when the device operates        in the contact mode of operation;    -   wherein the biometric sensor module further comprises a power        conditioning circuit coupled to the one or more contact        elements; the power-harvesting unit and at least one of the        internal components of the module; the power conditioning        circuit comprising:    -   a circuit path coupled at a first end to the one or more contact        elements and at a second end to the power harvest unit and said        at least one internal component of the module;    -   a switching element interconnecting a first part of the circuit        path comprising the first end and a second part of the circuit        path comprising the second end;    -   a bypass circuit providing a path that bypasses the switching        element, the bypass circuit permitting current to flow in a        direction from the first end to the second end of the circuit;        and    -   a coupling unit coupled to the first part of the circuit path        and the switching element;    -   the circuit being arranged so that: when the card is operating        in contact mode, power supplied through the contact elements        drives the switching element via the coupling unit to an open        configuration thereby limiting current to flow from the first        end to the second end of the circuit through the bypass circuit;        and when the card is operating in contactless mode, power        harvested by the power-harvesting unit causes the switching        element to adopt an open configuration thereby preventing        current flow from the second end of the circuit to the first end        of the circuit.

The bypass circuit may comprise a diode that limits current flow to thedirection from the first part of the circuit to the second part of thecircuit. The bypass circuit may further comprise one or more resistorelements arranged in series with the diode.

The power-conditioning circuit may contain only a single switchingelement. The switching element may be a bi-polar transistor. Theswitching element may be a PNP-transistor. The emitter of the transistormay be electrically connected to the first part of the circuit path, andthe collector may be electrically connected to the second part of thecircuit path.

The power conditioning circuit may further comprise a low-pass filter.The bypass circuit may form part of the low-pass filter thereby limitingcurrent to flow from the first end to the second end of the circuitthrough the low-pass filter when the card is in contact communicationwith the terminal and the switching element is in an open configuration.

The coupling unit may be a capacitor. The at least one internalcomponent of the module may be a power management unit.

BRIEF DESCRIPTION OF FIGURES

The present invention will now be described by way of example withreference to the accompanying drawings. In the drawings:

FIG. 1 shows a first example of a card architecture.

FIG. 2 shows a second example of a card architecture in which a moduleis connected to the card antenna.

FIG. 3 shows a third example of a card architecture in which a moduleand embedded chip are connected to the card antenna.

FIG. 4 shows an example implementation of a card adopting the cardarchitecture illustrated in FIG. 3.

FIG. 5 shows an example of a module comprising a power-conditioningcircuit.

FIG. 6 shows an example of a power conditioning circuit.

FIG. 7 shows a first example of a noise mitigation circuit to reducenoise fed back to the card reader.

FIGS. 8A and 8B show a second example of a noise mitigation circuit toreduce noise fed back to the card reader.

FIG. 9 shows a third example of a noise mitigation circuit to reducenoise fed back to the card reader.

FIG. 10 shows a fourth example of a noise mitigation circuit to reducenoise fed back to the card reader.

DETAILED DESCRIPTION

The present disclosure is directed to a device for contactless orcontact communication with a terminal. The device comprises an antennafor receiving a wireless signal emitted by the terminal; an embeddedchip (e.g. an integrated circuit chip) and an additional embeddedmodule. The module is separate from the chip (logically and/orphysically); for example they may be distinct components each embeddedwithin the device. The chip generates data for communication to theterminal to perform a first function associated with the device. Thisfirst function may be a base, or primary function of the device. Thechip could be, for example, a secure element. The module is configuredto perform processes as part of a second function associated with thedevice. Thus, the device is a multi-function device. The second functionmay be implemented by both the chip and the module; that is, theprocesses required to perform the second function may be distributedacross both the chip and the module. Alternatively, the processesrequired to perform the second function may all be performed by themodule; i.e. the module may perform the second function.

The device may be a smart card, and the terminal a card reader. In oneparticular implementation, the device is a smart card, such as bank orcredit card, and the primary function is the performance of a financialtransaction, such as making a purchase. The second function may be atype of biometric authentication. The biometric authentication mayauthenticate a user of the device to enable the completion of the firstfunction (e.g. performing a financial transaction). Alternatively, thesecond function may be the capture of an image of part of a user (e.g.,for the purposes of biometric authentication). Other exampleimplementations will be described in more detail below. The module isconnected to the antenna and comprises a power harvesting unitconfigured to harvest power from the wireless signal received by theantenna from the terminal. This harvested power is used to power atleast the module within the device. In some examples, the powerharvested by the module is used to power both the module and theembedded chip. In other examples, the antenna is shared by both theembedded chip and the module, with each of the chip and module includinga respective power-harvesting unit to harvest power from the wirelesssignal received by the antenna from the terminal.

Various internal architectures of multi-function devices will now bedescribed with reference to FIGS. 1 to 10. In each of these examples,the device is in the form of a smart card, and the terminal with whichit communicates is in the form of a card reader. This is for the purposeof illustration only, and it will be understood that each of thefollowing examples could be implemented in any suitable device capableof performing contactless and/or contact communication with a terminal.The following examples could for example be implemented within a deviceadopting a form factor that is not a card, for example a fob, a dongleor a security token (e.g. a USB token). Alternatively, the followingexamples could be implemented within devices integrated into acommunication device such as a mobile phone or smartphone; a wearabledevice, such as a bracelet, watch, a glove/pair of gloves, a pin (e.g. abrooch), a badge or some other contactless wearable device.

Each of these figures illustrates a card that can communicate with theterminal by both physical contact (by operating in a contact mode ofoperation), and without direct physical contact (by operating in acontactless mode of operation). These cards are referred to asdual-interface cards because they have a physical contact interface(e.g. in the form of a contact element) and a contactless interface(e.g. in the form of a contactless front end). The cards may beconfigured to communicate with the terminals according to any suitableradio communication standard when operating in contactless mode, forexample Near Field Communication (NFC). In each figure, the cardcomprises an embedded chip to perform a first function associated withthe card, and a separate module that operates to perform processes aspart of a second function associated with the card. The second functionmay be performed entirely by the module, or both the chip and module mayperform parts of the processing to perform the second function.

The architectures illustrated in these figures could be implementedwithin cards incorporating a variety of different functions. Forexample, the chip could implement banking functionality. Alternatively,the chip may operate to provide some other function associated with thecard requiring communication with a terminal, for example: providingphysical access of the card user to a region of an environment (e.g.building access); identifying or authenticating a user; retrieval ofpersonal user information (e.g. medical information and records) etc.The chip may be configured to communicate with the card reader inaccordance with the ISO14443 standard (when operating in contactlessmode) and the ISO7816 standard, as well as the EMVCo® standard. Themodule may provide some other function associated with the card thatdoes not require communication with a card reader. For example, themodule may be a biometric sensor module including one or more biometricsensors. The biometric sensor module may operate to perform biometricrecognition or authentication of one or more biometric parametersincluding, for example: fingerprint recognition; iris recognition; veinrecognition; retina recognition; voice recognition; behaviouralrecognition; facial recognition, etc. Alternatively, the module may be aPIN, or password generator, a movement or a position sensor, a displayscreen, a status indicator or a data input mechanism such as a keyboard.

FIG. 1 shows an example card 100 with a first type of internalarchitecture. The card comprises an antenna 104, a chip 106, a module108 and a contact element 118. In general, the card may comprise one ormore contact elements; a single contact element is shown here forclarity.

The chip is embedded within the card and could be, for example, a secureelement. Module 108 may also be embedded within the card. The module isa physically and/or logically distinct component from the chip 106. Eachof the chip 106 and module 108 may for example be implemented onrespective integrated circuit chips embedded in the card. The module 108and chip 106 are connected to each other by a link 110, such as a bus.

The contact element 118 is connected to the chip 106. The chip may beconnected to the contact element by a conductive link. The contactelement enables the card to communicate with the card reader throughdirect physical contact. The contact element provides electricalconnectivity to the card reader when the card and reader and broughtinto suitable physical contact. Thus, when the card is operating incontact mode, the chip receives power from the card reader through thecontact elements. The card may communicate with the card reader inaccordance with the ISO7816 standard when operating in contact mode.

The chip comprises a contact modem 120 that manages the transmission ofmessages to and reception of messages from the card reader whenoperating in contact mode. The contact modem 120 may also ensure thecommunications between the chip and card reader satisfy any relevantstandards (e.g. the ISO7816 standard) when the card operates in contactmode.

The antenna 104 is connected to the chip 106. The antenna is notconnected to the module 108. The chip comprises a power harvest unit 112that harvests power from the signal emitted from the card readerreceived by the antenna 104 when the card is operating in contactlessmode. The power-harvest unit 112 may for example induce a voltage fromthe received signal. That induced voltage can be supplied to othercomponents of the chip 106, and module 108. The chip further comprises areceiver/transmitter (Rx/Tx) modem 114 that manages the transmission ofmessages to and reception of messages from the card reader when incontactless mode. If communications between the card 100 and card reader102 are governed by one or more standards, the transceiver modem 114 mayoperate to manage the reception and transmission of those messages tocomply with the standards.

In the architecture shown in FIG. 1, only the chip 106 is connected tothe antenna 104, and consequently only the chip 106 harvests power fromsignals received from the card reader. The power up, subsequent powerconsumption of the module 108 during operation and power down istherefore controlled by the chip 106. The transmission of harvestedpower to the module 108 may be controlled by the power management unit116 of chip 106.

It has been appreciated that a problem with the architecture shown inFIG. 1 is that the module 108 is not readily capable of controlling ormanaging the amount of power it receives, because this is controlled bythe chip 106 independently of the module. However, in order to be ableto manage power to the module efficiently, it may be desirable to havedetailed knowledge of: (i) the timing and power requirements of themodule; (ii) the phase, or stage of processing at the module; and (iii)knowledge of available power within the field emitted by the cardreader. It is therefore likely to be challenging to implement effectivepower management of the module from the chip, particularly if the moduleand chip are supplied from different providers. A further problem withthe architecture shown in FIG. 1 is that it may require modification ofthe chip to make power available to the module. Such modifications tothe chip may be both expensive and time consuming, particularly if thechip is configured to comply with industry regulations and standardswith strict security requirements (such as ISO ISO14443, ISO7816, andthe EMVCo® standard).

FIG. 2 illustrates an alternative architecture within a multi-functioncard.

Card 200 comprises an antenna 204, embedded chip 206, a module 208 and acontact element 220. Module 208 may be embedded within the body of thecard 200. Module 208 is again a distinct component to the chip 206 (i.e.the module is logically and/or physically separate from the chip).Module 208 may for example be implemented within an integrated circuitchip separate to the chip 206. Module 208 and chip 206 are connected toeach other by a link 210. Link 210 could be a bus, for example.

The contact element 220 is connected to the chip 206. The chip may beconnected to the contact element by a conductive link. The contactelement enables the card to communicate with the card reader 202 throughdirect physical contact. The contact element provides electricalconnectivity to the card reader when the card and reader and broughtinto suitable physical contact. Thus, when the card is operating incontact mode, the chip receives power from the card reader through thecontact elements. The card may communicate with the card reader inaccordance with the ISO7816 standard when operating in contact mode.Power supplied from the reader in contact mode may be supplied to themodule 208 to power its internal components. The supply of power to themodule from the chip in contact mode may be controlled by a powermanagement unit 218 within the chip.

The chip may comprise a contact modem 222 that manages the transmissionof messages to and reception of messages from the card reader whenoperating in contact mode. The contact modem 222 may also ensure thecommunications between the chip and card reader satisfy any relevantstandards (e.g. the ISO7816 standard) when the card operates in contactmode.

When operating in contactless mode, the card 200 communicates with thecard reader 202 (e.g. transmits messages to and/or receives messagesfrom the card reader) through the antenna 204.

In the architecture shown in FIG. 2, only module 208 is connected toantenna 204; chip 206 is not connected to the antenna. Module 208comprises a power-harvest unit 212 configured to harvest power from thesignal received by the antenna 204 from the reader 202 when operating incontactless mode. In contrast to the architecture illustrated in FIG. 1,chip 206 does not include a power harvest unit because chip 206 is notconnected to the antenna 204, and thus cannot harvest power from thereceived signal. Power harvested by the power harvest unit 212 may besupplied to other components of the module 208. Power harvested by thepower harvest unit 212 may also be supplied to the chip 206. The module208 may supply power to the chip 206 to enable the chip to perform itsfunctions. This power may be supplied by link 210 or by a further link(not shown). The transmission of harvested power to the chip 206 may becontrolled by power management unit 216 of the module 208.

Because only module 208 is connected to the antenna 204, communicationswith the card reader 202 are performed by the module 208 when the cardoperates in contactless mode. That is, the module 208 controls andmanages the transmission of messages to, and the reception of messagesfrom, the card reader 202 in contactless mode. The control of messagesto and from the card reader 202 is performed by the Rx/Tx modem 214within module 208. As described above, communications between the card200 and card reader 202 may be governed by one or more standards. Insuch circumstances, the transceiver modem 214 may control the exchangeof messages with the card reader to comply with those one or morestandards. The standards may specify, for example, time windows for thetransmission and/or reception of messages; formats for the messages; oranti-collision and/or transmission protocols.

Data to be included in messages transmitted to the card reader 202 incontactless mode may be generated by the chip 206 during its operation.Similarly, data included within messages received by the module 208 maybe routed to the chip 206 (e.g. by link 210). In other words, the chip206 and card reader 202 may communicate or exchange messages via themodule 208 in contactless mode. Though the transceiver modem 214 thatmanages communications with the card reader is located within the module208, the module 208 itself may not generate data or messages that arecommunicated to the card reader 202. That is, only chip 206 may generatedata that is communicated to the card reader. In this regard, the chip206 may be referred to as a communication master, because it is the onlycomponent of the card in communication with the card reader (i.e. theonly component that processes received messages from the reader 202and/or generates message content for transmission to the reader). Insome examples, the messages communicated to the card reader 202containing data may also only be generated by the chip 206. The module208 (e.g., the transceiver modem 214 within the module) then operates tomodulate the messages onto the signal emitted by the card reader tocommunicate those messages to the card reader.

A further example architecture is illustrated in FIG. 3.

FIG. 3 shows a card 300. Card 300 comprises antenna 304, embedded chip306, a module 308 and a contact element 324. Module 308 is logicallyand/or physically separate to the chip 306. In the example shown, themodule is a distinct component to the chip 306 connected by link 310,which may be a bus, for example. Module 308 may be implemented within anintegrated circuit chip (ICC) separate to the chip 306. In otherexamples, the module and chip may be integrated on a single ICC, yet belogically separate. Card 300 communicates with the card reader 302 (e.g.transmits messages to and/or receives messages from the card reader)through the antenna 304 when operating in contactless mode, and throughthe contact element 324 when operating in contact mode. In general, thecard may comprise one or more contact elements; one contact element isshown here for the purpose of clarity.

The contact element 324 is connected to the chip 306 and the module 308,e.g. by conductive links. The contact element enables the card tocommunicate with the card reader through direct physical contact. Thecontact element provides electrical connectivity to the card reader whenthe card and reader and brought into suitable physical contact. Thus,when the card is operating in contact mode, the chip 306 and module 308receive power from the card reader through the contact elements. Powersupplied from the reader in contact mode may be supplied to the moduleand chip to power their internal components.

The antenna 304 is connected to both the chip 306 and the module 308.The antenna is shown connected to the chip 306 and the module 308 bypower line 312 that is routed from the antenna to both the chip and themodule. Power line 312 may be a physical line, e.g. a conductiveelement.

Chip 306 includes a power harvest unit 314. The power harvest unit isoperable to harvest power from the signal received by the antenna 304when the card operates in contactless mode. Power harvested by unit 314may be supplied to other components of the chip 306 to power thosecomponents.

Chip 306 further includes a power management unit (PMU) 318. The PMU 318operates to manage, or control, the use of power (either harvested bythe power harvest unit 314 in contactless mode or supplied through thecontact element 324 in contact mode) by components of the chip. The PMU318 may control the power consumed by the other components of the chipto perform their tasks.

The module 308 includes its own power harvest unit 316. The powerharvest unit 316 is operable to harvest power from the signal receivedby the antenna 304 in contactless mode. Power harvested by unit 316 maybe supplied to other components of the module 308 to power thosecomponents. The presence of power harvest unit 316 within the module 308enables the module to harvest power from signals received from thereader 302 separately from the chip 306.

Module 308 also includes its own power management unit 320 to manage, orcontrol, the consumption of power (either harvested by the power harvestunit 316 in contactless mode or supplied through the contact element 324in contact mode) by components of the module. The PMU 320 may controlthe power consumed by the other components of the module 308 duringtheir operation to perform their tasks.

Because the contact element 324 is connected to both the chip 306 andthe module 308, and the antenna 304 is also connected to both the chip306 and module 308, the chip and module can both receive or harvestpower from the reader separately of each other. However, only the chip306 is capable of communicating with the reader. That is, only the chip306 can generate and transmit messages to the reader (e.g., by loadmodulating the signal emitted by the reader). Likewise, the chip 306 isthe only component on the card 300 that can receive and process messagescommunicated from the reader (e.g. by demodulating the signal receivedby the antenna). In other words, only chip 306 generates data that iscommunicated to the reader 302. Thus, while in some examples the module308 may generate and communicate data to the chip 306, the module 308does not communicate (either directly or indirectly) with the reader302. Put another way, data generated by the module 308 may remainlocally on the card 300.

The control of messages to and from the card reader 302 (and morespecifically, between the chip 306 and reader 302) is performed by theRx/Tx transceiver modem 322 and contact modem 326 within the chip 306.The transceiver modem 322 controls the communication of messages withthe reader 302 in contactless mode, and the contact modem 326 controlsthe communication of messages with the reader 302 in contact mode.

The transceiver modem 322 may for example control the exchange ofmessages with the card reader 302 to comply with one or more standardsgoverning the communication between card 300 and reader 302 (e.g. theISO14443, ISO7816 and EMVCo® standards). The standards may specify, forexample, time windows for the transmission and/or reception of messages;formats for the messages; or anti-collision and/or transmissionprotocols. The transceiver modem 322 may also be responsible for loadmodulating messages generated by the chip 306 onto the signal emitted bythe reader 302 to communicate those messages to the reader, anddemodulating the signal received by the antenna 304 to decode messagesreceived from the reader.

The contact modem 326 may similarly control the exchange of messageswith the card reader 302 to comply with the standards governingcommunications between the card and reader in contact mode (e.g. theISO7816 and EMVCo® standards).

The architecture illustrated in FIG. 3 may conveniently present severaladvantages over the architecture illustrated in FIG. 1.

Firstly, because the antenna 304 is shared by both the chip 306 and themodule 308, and both chip 306 and module 308 include respective powerharvesting units, the module 308 can harvest power from the receivedsignal independently of the chip 306 in contactless mode, e.g.independently of the operation of the chip. Furthermore, because thechip 306 and module 308 include respective power management units, themodule 308 and chip 306 can control and manage the power consumption ofrespective internal components independently of each other. This canenable greater control of the processing tasks and functions carried outby various components of the chip and module, which can be particularlyadvantageous in implementations when the power harvested from the cardvaries over the typical time required to perform those tasks andfunctions (e.g. due to variations in the physical position of the cardin space); and/or when the communications between the card and readerare tightly regulated, for example when the card communicates with thereader to perform banking functions, in which case communications mustsatisfy, amongst others, the EMVCo® standard. The independent controland management of power consumption of the chip 306 and module 308 alsoenables the both the chip and module (or substituent components thereof)to be powered down, or put in a low-power mode when they are not needed,leading to greater power savings compared to what can be achieved withthe architectures shown in FIGS. 1 and 2, where such independent controlis not possible.

Secondly, enabling both the chip 306 and the module 308 to access andharvest power from the antenna independently of each other reduces thecomplexity of controlling the power management of the two components. Asdescribed above, effective power management of the module 308 mayrequire knowledge of parameters including the timing and powerrequirements of the module, knowledge of the available power that can beharvested from the signal emitted from the card reader, and knowledge ofthe various phases, or stages, of the module's processing. That is,effective power management of the module 308 may require local knowledgeof the module and its operation. Enabling the module 308 to manage itspower separately of the chip 306 therefore simplifies the implementationof an effective power management strategy of the module.

Thirdly, connecting the module 308 to the antenna 304 enables the moduleto harvest power from the received signal without requiring input orcontrol from the chip 306, meaning the fundamental operation of the chipcan remain unchanged compared to the situation in which the module 308is not present on the card. This is convenient because in certainimplementations where the communication between the chip and reader istightly regulated, modification to the connections or operation of thechip (e.g. by enabling access to the chip from further components) maybe restricted, or technically complex to implement. Adopting thearchitecture illustrated in FIG. 3 can enable a card containing a chipimplementing a base, or primary function to be more readily adapted tocontain an additional module implementing a secondary, or additionalfunction because substantial modification to the chip can be avoided.

The architecture illustrated in FIG. 3 may also provide advantages overthe architecture illustrated in FIG. 2.

The architecture illustrated in FIG. 3 enables the Rx/Tx modem to remainwithin the chip 306. This is particularly convenient because includingthe Rx/Tx modem within the module (as in card 200) may present severalchallenges. For example:

-   -   (i) including the Rx/Tx modem within the module may enable the        module to manipulate communications between the card and card        reader, or introduce disturbances to otherwise manipulate the        outcome of the primary function of the card, giving rise to        security concerns. Thus, when the card and card reader are        configured to comply with communication protocols having        relatively strict security requirements (such as EMVCo®),        implementing the Rx/Tx modem within the external module would        likely impose additional security requirements on the module        than may otherwise be required.    -   (ii) Communications between the chip and card reader would        require messages to be sent over link 210, which may consume        additional power, bandwidth and introduce additional latency.    -   (iii) The Rx/Tx modem is a relatively complex component that may        require specialist knowledge for effective implementation        (particularly when compliance with the ISO14443, ISO7816, and        the EMVCo® standards is desired). The inclusion of the Rx/Tx        modem within the module therefore increases its complexity,        which may have practical implications when the chip and module        are supplied by different providers.

The architecture of FIG. 3 is also more readily compatible with thecontact mode of operation compared to the architecture shown in FIG. 2.In the architecture shown in FIG. 2, the modem for contact modecommunications is located within the chip 206, whereas the modem forcontactless mode communications is located within the module 208. Aconsequence of this is that the communication path for messagesexchanged between the card and card reader is different for the twomodes of operation, which may for example lead to more complex routingstrategies. In contrast, in the architecture shown in FIG. 3, both thetransceiver modem 322 and the contact modem 326 are located within thechip 306, which means the communication path for messages exchanged withthe card reader is the same for both the contact mode and thecontactless mode.

It will be appreciated that the cards illustrated in FIGS. 1-3 mayinclude additional components not shown in the figures. For example,both the chip and the module may include dedicated microcontroller units(MCUs).

FIG. 4 shows a more specific implementation of a card adopting thearchitecture illustrated in FIG. 3.

FIG. 4 shows a card 400. The card 400 comprises an antenna 404, anembedded chip in the form of a secure element 406, and a module in theform of a biometric sensor module 408. When the card operates incontactless mode, the antenna 404 receives the wireless signal emittedby the reader 402 when the card is in sufficient proximity to thereader. In this particular example, the signal emitted by the reader isan NFC signal. Thus, the card and reader communicate in accordance withthe NFC radio communication standard. Contactless communication betweenthe card 400 and reader 402 may also comply with the ISO/IEC 14443standard and ISO/IEC 7816 standards. In this regard, the reader 402 maybe referred to as a proximity coupling device (PCD), and the card 400may be referred to as a proximity integrated circuit card (PICC).

The secure element 406 and sensor module 408 are logically and/orphysically separate components of the card 400. If physically separate,they may be not implemented on a common chip but instead implemented onseparate respective chips each embedded within the card. If onlylogically separate, they may be implemented on a common chip. In theexample shown here, they are physically separate.

The secure element 406 and sensor module 408 are interconnected by alink 430. Link 430 could be a bus, for example the inter-integratedcircuit (I²C) bus.

Antenna 404 is shared between the secure element 406 and the biometricsensor module 408. That is, both the secure element and the biometricsensor module are connected to the antenna. The card comprises a powerline 410 that is routed from the antenna to both the secure element andthe biometric sensor module to connect those components to the antenna.The power line may be a physical line, such as a conductive wire.

Card 400 also comprises one or more contact elements 412 to enable thecard to communicate with the reader 402 through direct physical contact.The contact elements provide electrical connectivity to the card reader402 when the card and reader and brought into suitable physical contact.Contact communication between the card and card reader may be governedby the ISO/IEC 7816 standard. When the card is operating in contactmode, the secure element 406 and module 408 receive power from the cardreader 402 through the one or more contact elements 412 over link 434.

The secure element 406 operates to perform a first function associatedwith the card 400. As part of performing this function, the secureelement exchanges data with the card reader. This data is exchangedthrough the contactless interface when the card is operating in acontactless mode, and through the contact interface when the card isoperating in contact mode. The secure element comprises a contactlessfront end 414, a transceiver modem 416, a secure microcontroller unit(MCU) 418, a power management unit 432 and a contact modem 436. Thecomponents of the secure element may be interconnected by a bus.

The contactless front end 414 operates to harvest power from thewireless signal emitted by the reader 402 and received by the antenna404 when the card is operating in contactless mode. The contactlessfront end may operate to harvest power from the received signal andoutput a rectified voltage to other components internal to the secureelement, i.e. to the transceiver modem 416, power management unit 432and the MCU 418. The contactless front end is an example of a powerharvest unit.

The power management unit 432 manages, or controls, the power suppliedto the components of the secure element that is harvested by thecontactless front end or supplied through the contact element 412. Inthis way, the power management unit 432 can control the power consumedby the other components of the secure element. The power management unit432 may be physically interconnected to each of the contactless frontend 414; modem 416 and 436; and the MCU 418.

The transceiver modem 416 operates to extract data from a receivedwireless signal when the card operates in contactless mode. The reader402 transfers data to the card 400 by modulating the signal itgenerates. The reader may modulate the generated signal by means ofamplitude modulation. The modem may then extract data from the receivedwireless signal by demodulating amplitude variations of the voltageinduced in the antenna caused by the amplitude modulation at the reader402.

The modem 416 may also operate to transfer data and messages from thesecure element to the card reader 402 when the card is operating incontactless mode. The modem may transfer messages to the reader bymodulating data generated within the secure element onto the wirelesssignal emitted from the reader. To do this, the modem 416 applies amodulated load to the antenna 404. Modulating the antenna load at thecard 400 varies the power drawn from the received signal in accordancewith the modulation. The variations in drawn power can be detected bythe reader 402 and interpreted as data communicated from the card. Thisprocess may be referred to as load modulation.

The modem 416 may also be responsible for controlling the transmissionof messages from the secure element to the reader to comply with theISO/IEC 14443 and ISO/IEC 7816 standards. The modem 416 is therefore anexample of a transmission management unit.

The contact mode modem 436 operates to transfer and receive data andmessages from the secure element to the card reader 402 when the card isoperating in contact mode. The contact mode modem may exchange messageswith the card reader 402 via the contact element 412. The contact modemodem may control the transmission of messages from the secure elementto the reader to comply with the ISO/IEC 7816 standard.

The MCU 418 may operate to store data (e.g. data received from thereader 402 and/or data generated internally of the secure element orreceived from the sensor module 408). The MCU may also operate toperform one or more tasks (e.g. encryption and/or authentication) toimplement a first and/or second function associated with the card.

The biometric sensor module 408 operates to perform processes as part ofa second function associated with the card. In this example, thatfunction is biometrically identifying or authenticating a user of thecard 400. In some examples, the module 408 performs all the processesforming the biometric authentication; i.e. the module 408 performs thebiometric authentication. In other examples, the processes required toperform the biometric authentication are distributed between the module408 and the chip 406; i.e. both the chip and the secure element performprocesses required to perform the biometric authentication. Examples ofthis will be described in more detail below.

In contrast to the secure element 406, the biometric sensor module doesnot exchange data with the card reader. The sensor module 408 comprisesa contactless front end 420; a power management unit 422; amicrocontroller unit (MCU) 424; a biometric sensor 426 and anapplication specific integrated circuit (ASIC) 428. The components ofthe sensor module 408 may be interconnected by a bus.

The contactless front end 420 operates in a similar manner to the frontend 414, and harvests power from the wireless signal emitted from thecard reader and received by the antenna 404 when the card operates incontactless mode. Because both the secure element 406 and the biometricsensor module 408 are connected to the antenna and include their owncontactless front end, the biometric sensor module 408 is able toharvest power from wireless signals received at the antennaindependently of the secure element 406.

The contactless front end 420 outputs harvested power to othercomponents of the biometric sensor module 408. The contactless front endmay operate to output a rectified voltage from power harvested from thereceived signal. The rectified voltage may be supplied to other internalcomponents of the sensor module 408. In one particular arrangement, thecontactless front end outputs the rectified voltage to the powermanagement unit 422. The power management unit may be the only componentof the biometric sensor module 408 that receives power from thecontactless front end 420 in contactless mode.

The power management unit 422 manages, or controls, the power suppliedto the components of the biometric sensor module 408. In this way, thepower management unit 422 can control the power consumed by the othercomponents of the sensor module. When the card operates in contactlessmode, the power management unit 422 receives harvested power from thecontactless front end 420.

When the card operates in contact mode, the power management unit 422receives power supplied from card reader 402 through the contact element412. Thus, the power management unit may be connected to the contactelement (e.g. by a conductive link).

The power management unit 422 may be physically interconnected to eachof the MCU 424, sensor 426 and ASIC 428. This allows the powermanagement unit to control the power supplied to each of thesecomponents separately. The inclusion of the power management unit 422within the sensor module 408 also enables the sensor module to controlthe power consumption of each of its internal components independentlyof the secure element 406.

Sensor 426 is a biometric sensor for capturing images of a biometricsource. Sensor 426 could be, for example, a fingerprint sensor, a retinasensor, an iris sensor, a facial sensor etc.

The ASIC 428 controls the operation of the sensor 426. The ASIC may forexample instruct the sensor to enter an acquisition mode in which thesensor captures an image of a biometric source (e.g. a fingerprint,retina, iris etc.). The ASIC may also receive image data captured by thesensor 426 (e.g. during acquisition mode). The ASIC may communicate thecaptured image data to the MCU 424. Following capture of the image, theASIC may also instruct the sensor to power down to a standby mode.

The MCU 424 may perform image matching to compare an image captured bythe sensor 426 to a stored template image, or to stored template images.A template image is a trusted image. An image may be trusted in thesense it is taken to be of a biometric source belonging to the user ofthe card 400. To perform the image matching, the MCU may perform featureextraction on the captured image to identify a set of one or moreextracted features. The extracted features are then compared with thefeatures of the template image to determine if the captured imagematches the template image. The MCU may for example compare the featuresof the images to determine a matcher score for the captured image. Thecaptured image may be taken to match the template image if the matcherscore is above a predetermined threshold.

The MCU may communicate an indication that the captured image matchesthe template image to the secure element 406. The secure element 406 canthen communicate an indication that the user of the card has beenauthenticated back to the reader 402. The authentication of the carduser may enable the primary function associated with the card 400 to becompleted. Alternatively, the MCU may communicate to the secure element406 that the captured image does not match the template image, in whichcase the user of the card has not been authenticated and primaryfunction associated with the card 400 may not proceed, or may proceed inan altered fashion as a consequence of there being no match. This is anexample of an implementation in which each stage, or process, of thebiometric authentication is performed by the module 408.

In an alternative implementation, the process of performing the imagematching may be performed by the MCU 418 within the secure element 406,rather than by the MCU 424. This is an example of an implementation inwhich the processes of biometric authentication are performed by boththe secure element 406 and the module 408; i.e. the biometricauthentication is not performed solely by the module 408.

FIG. 5 shows a further example of a module. The module 508 is shownconnected to an antenna 504, and a contact element 512. The chip (e.g.secure element) has been omitted for the purposes of clarity. Module 508could be implemented within the architectures shown in FIG. 3 or 4.

Module 508 comprises a contactless frontend (CLF) 520, a powermanagement unit 522, an MCU 524, sensor 526 and ASIC 528. Thesecomponents may operate in the same manner as the correspondingcomponents shown in FIG. 4. The module 508 further comprises a contactpower conditioning circuit 530. The power conditioning circuit isconnected to the contact element 512 by link 532. Link 532 may be aconductive link.

The power conditioning circuit 530 performs two functions. Firstly, itcan operate to prevent current inrush from overloading the card readerwhen the card is operating in contact mode. Current inrush refers to thecurrent drawn by the card when the components of the card are poweredup, e.g. when the card is inserted into the card reader in contact mode.Conventional card readers are typically only designed to power thesecure element on the card, rather than a secure element plus anadditional module. As a consequence, the card readers may detect a faultif an amount of current is drawn on power up that exceeds apredetermined threshold. It has been appreciated that the inclusionwithin the card of the module increases the current drawn on power up topower up the internal components of the module, thus increasing the riskthat the drawn current will overload the card reader, causing a fault tooccur. The power conditioning circuit operates to limit the currentdrawn by the module through the contact element during power up when thecard is operating in contact mode. This will be explained in more detailbelow.

Secondly, the power conditioning circuit operates to isolate the contactelement from power harvested in the module during contactless operation.It has been appreciated that when the module harvests power from thesignal emitted from the card reader using its contactless front end,that harvested power may additionally power the contact element, causingthe secure element to erroneously detect that the card is operating inits contact mode of operation.

An example power conditioning circuit is shown in FIG. 6. The powerconditioning circuit is denoted generally at 600, and is shown connectedto both the contact element 512 and the module's contactless frontend(CLF) 520. The circuit is also coupled to an internal component of themodule, which in this example is the module's power management unit 522.

The circuit comprises a through-path 602 comprising a first path 604 anda second path 606 interconnected by a switching element 608. Switchingelement 608 is a bi-polar transistor. In particular, in this exampleswitching element 608 is a PNP transistor that includes an emitter, abase and a collector. The emitter is electrically connected to the firstpath 604, and the collector is electrically connected to the second path606. The through path 602 extends between the contact element 512 andthe contactless frontend 520. Thus, the first path 604 extends betweenthe contact element 512 and the switching element 608, and the secondpath extends between the switching element 608 and the contactlessfrontend 520. In the current example, where the switching element is aPNP transistor, the first path extends between the contact element 512and the emitter of the PNP transistor, and the second path extendsbetween the collector of the PNP transistor and the contactless frontend520.

The circuit further comprises a bypass route 610 arranged in parallel tothe switching element 608. The bypass route is therefore connected toboth the first path 604 and the second path 606. The bypass route 610 inthis example includes a resistor 612 and diode 614. In other examples itmay comprise multiple resistors arranged in series. The diode 614 has aforward direction from the contact element 512 to the contactlessfrontend 520 (and thus a reverse direction from the contactless frontendto the contact element). The bypass route permits current to flow fromthe first path to the second path without passing through switchingelement 608 (i.e., by bypassing switching element 608).

The circuit further comprises a coupling unit 616 that couples the firstpath 604 to the base of the switching element. The coupling unit has afirst terminal connected to the first path 604 and a second terminalcoupled to the base of switching element 608, and to ground via aresistor 618. The coupling unit 616 is therefore located on thecontact-element-side of the bypass route 610 and the switching element608. In this example, the coupling unit is a capacitor. The couplingunit operates to pass time-varying current supplied from the contactelement.

The circuit further comprises a resistor 620 arranged between the firstpath 604 and ground. The resistor 620 is arranged on thecontact-element-side of the capacitor 616.

On the CLF-side of the switching element 608, there is provided aresistor 622 and capacitor 624. A first terminal of capacitor 624 iscoupled to the second path 606, and the second terminal of the capacitoris connected to ground. Resistor 622 is located between the output ofdiode 614 and the first terminal of the capacitor 624.

As will be explained in more detail below, resistors 612, 622 andcapacitor 624 form a low-pass filter 626. In the current example, inwhich switching element 608 is a PNP transistor, the resistor 622 mayalso be said to be located between the collector of PNP transistor 608,and the first terminal of the capacitor 624.

It is noted that circuit 600 contains only a single switching element.

Circuit 600 can operate in a forward direction mode and a reversedirection mode. When operating in the forward direction mode, thecircuit controls the flow of current from the contact element 512 to themodule's PMU 522 during power-up and following power-up. That is, thecircuit controls the amount of current drawn by the PMU 522 from thecontact element. The circuit operates in forward direction mode toprevent current inrush from overloading the card reader when the card isoperating in contact mode. When operating in reverse direction mode, thecircuit controls, or isolates, the flow of current from the CLF 520 backto the contact element 512 when the card is operating in contactlessmode. In other words, the circuit operates in reverse direction mode toisolate the contact element from power harvested by the module'scontactless frontend. These operating modes will now be described inmore detail.

When the card is operating in contact mode then, during power up (e.g.as the card is inserted into the card reader), power is supplied fromthe card reader through the contact element (e.g. in accordance with theISO7816 standard). This initial supplied power pulls the first path 604high. Coupling capacitor 616 couples the supplied power to the base ofthe switching element 608, pulling the base high and causing switchingelement 608 to be open. By driving the switching element open, thenduring power up power can only pass from the first circuit path 604 tothe second circuit path 606 through the bypass circuit 610; in otherwords, the bypass circuit forms the only path between the first circuitpath 604 and the second circuit path 606.

As mentioned above, resistors 612, 622 and capacitor 624 form a low-passRC filter network. The bypass circuit 610 therefore forms part of thelow-pass RC filter network. Thus, by driving switching element 608 open,current supplied from the contact element passes through the bypasscircuit 610 and the low-pass filter network. The low-pass filter networkoperates to slow down the current inrush during power up, reducing thepeak current inrush value. Thus, the circuit 600 controls the currentdrawn from the contact element by the PMU 552 to prevent current inrushfrom overloading the card reader. The amount of current drawn by the PMUduring power up can be controlled by suitable resistance selection ofthe resistors 612 and 622, and capacitor 624.

In time, coupling capacitor 616 is charged by the contact element 512,causing the base of switching element 608 to be pulled low by resistor618. Thus, following power-up, switching element 608 is pulled closed byresistor 618, and thus current from the contact element 512 is suppliedfrom the first circuit path 604 to the second circuit path 606 (andconsequently to the PMU 522) through the switching element 608.

The reverse mode of operation (when the card is operating in contactlessmode) will now be described.

When the card is operating in contactless mode, the module's contactlessfrontend 520 operates to harvest power from the signal emitted from thecard reader, as described above. When the card is operating incontactless mode, no power is drawn through the contact element 512.Switching element 608 is therefore open, because its base is notnegatively biased with respect to the emitter. The switching element 608and bypass circuit 610 therefore prevent current flowing from the secondcircuit path 606 to the first circuit path 604. In other words, duringthe contactless mode of operation, power harvested from the CLF 520 isisolated from the contact element 512 by: (i) the open switchingelement; and (ii) the bypass circuit, whose diode 614 prevents currentflowing from the second circuit path 606 to the first circuit path 604.

The arrangement of circuit 600 provides several advantages.

Firstly, circuit 600 operates to both prevent current inrush fromoverloading the card reader when the card is operating in contact mode,and to isolate the contact element from power harvested by the module'scontactless frontend during the contactless mode of operation, yetcontains just a single switching element, reducing the cost andcomplexity of introducing the power conditioning circuit within themodule. Circuit 600 can therefore be implemented with a reduced numberof components compared to approaches in which separate circuits areimplemented to perform current inrush prevention and contact elementisolation. Reducing the component count can also reduce the cost of thecircuit.

Secondly, the efficient use of components of the power conditioningcircuit means the circuit can be implemented on a relatively smallphysical scale. This is convenient because packaging constraints on thecard may be relatively high. For example, it may be desirable for themodule to be as physically small as possible so as to not substantiallyincrease the thickness and/or weight of the card.

Thirdly, the use of a single switching element which may be in the formof a PNP transistor may facilitate the provision of a power conditioningcircuit suffering from only a relatively low voltage drop across itcompared to other possible implementations (e.g. implementationsemploying multiple switching elements, or implementations using onlydiodes to control the directional flow of current). Reducing voltagedrop enables a higher voltage to be available for other components ofthe module, such as the biometric sensor. This may be particularlyadvantageous for examples in which the biometric sensor is a capacitivefingerprint sensor, since higher levels of available voltage leads toimproved signal-to-noise ratios and hence better-quality image capture.Improving the image capture can lead to improved false rejection/falseacceptance rates when the device is used for biometric verification.

In summary, FIGS. 2 to 5 describe various architectures in which thecard antenna is connected to a module that is logically and/orphysically separate from the embedded chip that exchanges data with thereader. As explained above, data can be communicated from the card backto the reader by load modulation of the signal emitted by the readerwhen the card operates in contactless mode. In effect, data is modulatedonto the signal emitted by the reader by varying the power drawn fromthe signal at the card. It has been appreciated that additionalcomponents of the card drawing current from the emitted signal (such asthe module in the architecture shown in FIGS. 2 to 4) will affect theload modulation of the emitted signal, which may appear as extra noiseto the reader.

The introduction of extra noise at the card reader may be problematic,particularly when communications between the card and reader are tightlyregulated to comply with industry standards.

To combat the impact of the module on the load modulation when the cardoperates in contactless mode, the cards 200, 300, 400 may additionallycomprise noise mitigation circuitry. In summary, the noise mitigationcircuitry operates to store charge as the card is brought into range ofthe reader. Brought into range means that the card is brought intosufficient proximity of the reader for a voltage to be induced by thecard antenna from the signal emitted by the reader. Subsequent currentdraws resulting from operation of the components within the module canthen first be supplied by the noise mitigation circuitry before power isdrawn from the signal received at the antenna. This reduces the impactof the module on the load modulation of the emitted signal. Though theinitial charging of the noise mitigation circuitry may result in loadspikes on the emitted signal, it has been appreciated that this ingeneral is more tolerable during start-up of the card components (i.e.when the card is first brought into proximity of the card reader)because power spikes resulting from power up is expected and can behandled by appropriate start-up circuitry within the card.

FIG. 7 shows a first example of noise mitigation circuitry 700.Circuitry 700 may be included within the power harvest unit 212, powerharvest unit 316, or contactless frontend 420, 520. The remainingcomponents of those units have been omitted from FIG. 7 for clarity.

The circuitry 700 comprises first and second inputs 702 and 704 from thecard antenna, and a first capacitor 706. The capacitor 706 is positionedacross the two inputs 502 and 504. Capacitor 706 is a tuning capacitorthat tunes the antenna (not shown) to the frequency of the signalemitted by the card reader. In some examples, the signal emitted by thecard reader may be an NFC signal at a frequency of 13.56 MHz.

The circuit 700 further comprises rectifier circuitry 708 and supplyregulation circuitry 710. The rectifier circuitry is coupled to theterminals of the capacitor 706. The rectifier circuitry operates torectify the voltage induced by the antenna. The supply regulationcircuitry operates to output a stable, regulated voltage. It maycomprise a low drop-out regulator.

The circuit 700 further comprises a plurality of charging elementsconfigured to store charge. In this example, the charging elements arecapacitors. The circuit includes two capacitors 712 and 714. Capacitor712 is located between the rectifier circuitry and supply regulationcircuitry. Capacitor 714 is coupled to the output of the supplyregulation circuitry. Capacitors 712 and 714 are charged as the card isbrought into range of the reader by the voltage induced by the antenna.Capacitor 712 is charged by rectifier circuitry 708, and the capacitor714 is charged by the supply regulation circuitry 710. The capacitors712 and 714 discharge to supply current to components of the module(e.g. the power management unit 422) in response to a current demandfrom those components during operation. In other words, capacitors 712and 714 operate as energy stores that are charged as the card is broughtinto proximity of the reader, and then discharge to supply a peakcurrent demand to components of the module. Thus, circuit 700 operatesto prevent current demands from components of the module from modulatingthe load on the signal emitted by the reader, which in turn reduces thelevel of noise at the reader from the operation of the module. Capacitor712 also functions as a smoothing capacitor to the rectifier circuitry708. It may additionally function as a filter to filter out noise fromreaching the antenna.

A further example of the noise mitigation circuitry is shown in FIGS. 8Aand 8B.

FIG. 8A shows a local supply decoupling circuit 802 and 804 for themodule's MCU 424 and sensor 426 respectively. The remaining componentsof the module that are connected to the MCU and sensor have been omittedfor clarity.

Local supply decoupling circuits 802 and 804 each comprise a capacitor,or a plurality of capacitors arranged in parallel. In this example, eachlocal supply decoupling circuit comprises two capacitors arranged inparallel. The capacitors are charged from the voltage induced by theantenna as the card is brought into range of the reader. In the eventthe module's power harvesting circuitry includes supply regulationcircuit 700, the capacitors may be charged by supply regulationcircuitry 710.

Subsequent current draws resulting from operation of the MCU 424 andsensor 426 can then first be supplied by the local supply circuits 802and 804. If the power harvesting circuitry additionally includes supplyregulation circuit 700, current can then be drawn from capacitors 714and 712 after being drawn from the local supply circuits 802 and 804. Inother words, current draws by the MCU 424 and sensor 426 can be suppliedin the following order: 1) initially from local supply circuits 802 and804 respectively; 2) thereafter, from the capacitor 714 of theregulation circuit 700; and 3) thereafter, from the capacitor 712 of theregulation circuit 700. This sequential supply of demanded currentconveniently reduces the load modulation on the signal emitted by thereader.

The routing of the capacitors in supply circuits 802, 804 is illustratedin FIG. 8B. The interconnect circuitry connecting the MCU/sensor to thepower management unit 422 is shown at 806. It is noted that forsimplicity, a single block representing either the MCU or sensor isillustrated in FIG. 8B. Equivalent interconnect circuitry will connectboth the MCU and sensor to the power management unit.

It can be seen that the interconnect circuitry defines two supply railsVDD and VSS to the MCU/sensor. Supply rail VSS is input into a firstterminal end of the local decoupling circuit, and supply rail VDD isinput into a second terminal end of the local decoupling circuit. Thetwo supply rails and local decoupling circuits therefore form a closedcircuit with the MCU/sensor. This closed circuit enables currentdemanded from the MCU/sensor to be supplied by the local supply circuitwhilst reducing the current supplied by the power management unit 414.

The capacitors of each local decoupling circuit also operate to filternoise bands generated from the sensor/MCU. If each local decouplingcircuit includes multiple capacitors arranged in parallel, eachcapacitor may have a different capacitance to filter out differentrespective noise bands.

FIG. 9 shows a further example of a noise mitigation circuit 900. Noisemitigation circuit 900 operates to maintain an approximately constantcurrent load on the antenna. That is, the circuit operates to counteractdeviations in current load seen at the antenna plane. In contrast to thecircuits shown in FIGS. 7 and 8, which may be more suitable forrelatively large current spikes, the circuit shown in FIG. 9 may be moresuitable for more slowly varying current loads.

Circuitry 900 may be may be included within the power harvest unit 212,power harvest unit 316, or contactless front end 420, 520. The remainingcomponents of those components have been omitted from FIG. 9 forclarity.

The circuitry 900 comprises first and second inputs 702 and 704 from thecard antenna, and a first capacitor 706 as described above withreference to FIG. 7. The circuit further comprises rectifier circuit 708and supply regulation circuit 710 as described above with reference toFIG. 7. The circuit additionally comprises control circuitry 902.

Control circuit 902 comprises a current sense and control block 904, anda variable load 906, e.g. a resistor. The current sense and controlblock 904 detects deviations in current demanded by other components ofthe module (e.g. the power management unit 422). The block 904 thencontrols the current supplied from the supply regulation circuit 710 andcapacitor 714 in dependence on measured deviations of demanded current.The block 904 does this by suitable control of the resistance ofvariable load 906. Thus, the circuit 900 supplies a variable level ofcurrent to the other components of the module in response to deviationsin demanded current so as to present a constant current demand to theantenna. This reduces the level of noise fed back to the reader.

FIG. 10 shows a further example of noise mitigation circuitry 1000implemented as part of an alternative power management architecture. Inthis example, the supply regulation block 710 shown in FIGS. 7 and 9 hasbeen replaced with a first and second type of voltage regulator eachconnected to a respective component of the module (which, for thepurposes of illustration, is taken as module 408). The circuit comprisesa first branch and a second branch each connected to a common node thatis coupled to the rectifier circuit 708. The first branch comprises afirst type of voltage regulator coupled to a first component of themodule, and the second branch comprises a second type of voltageregulator coupled to a second component of the module. In this example,the first type of voltage regulator is a low dropout regulator (LDO)1002, and the second type of voltage regulator is aswitch-mode-power-supply (SMPS) 1004. The LDO 1002 is coupled to themodule's ASIC 428, and the SMPS 1004 is coupled to the module's MCU 424.

The circuit 1000 further comprises a first charging element 1006 locatedbetween the LDO 1002 and the ASIC 428, and a second charging element1008 between the SMPS 1004 and the MCU 424. The charging elements inthis example are capacitors.

The two voltage regulators 1002 and 1004 operate to output differentregulated voltage levels from each other. In one particularimplementation found to be convenient for a smartcard application, thevoltage regulator 1002 may output a regulated voltage of approximately2.5V, and the voltage regulator 1004 may output a regulated voltage ofapproximately 1.8V; i.e., the first type of voltage regulator outputs ahigher regulated voltage than the second type of voltage regulator.These different levels of regulated voltage enable different currentlevels to be supplied to the two components 424 and 428. This isconvenient because it has been appreciated that the processing speed ofthe MCU 424 is a function of supplied current. By increasing the currentsupplied to the MCU 424, its processing speed can be increased. Anumerical illustration of how circuit 1000 achieves this will now bedescribed.

An equal wattage is supplied to both branches of the circuit from therectifier circuit 708. As mentioned, the LDO 1002 in this exampleregulates the voltage to 2.5V. A typical example of the current in thiscase is taken to be 10 mA, for the purpose of illustration. This gives avalue of 25 mW supplied by the LDO 1002. The SMPS 1004 is known to havea typical efficiency rating of around 90% compared to the LDO. Thus, thewattage supplied to the MCU 424 (on the assumption that equal wattage issupplied to both the LDO 1002 and SMPS 1004 from the rectifier circuit)is equal to 25 mW×90%=22.5 mW. If the SMPS regulates the output voltageto 1.8V, this gives a current value along the second branch of 12.5 mA.That is, the current along the second branch of circuit 1000 is higherthan the current along the first branch of circuit 1000 due to the lowerregulated voltage.

Calculations by the inventors have found that, for a supplied current of10 mA, the MCU 424 can operate with a clock speed of approximately 60MHz. However, for a supplied current of 12.5 mA, the MCU 424 can operatewith a clock speed of approximately 75 MHz, which would result inapproximately a 20% reduction in execution time.

Thus, compared to the circuit 700 of FIG. 7, the circuit of FIG. 10enables the current supplied to the MCU 424 to be increased (with aconsequential enhancement of processing speed), whilst still enablingthe module's ASIC 428 to receive the higher output regulated voltagefrom the LDO 1002 (which may be needed to maintain optimal performanceof the ASIC).

Examples have been described herein in which the device is a smart card.It will be understood that the term ‘card’ does not imply anyconstraints with regards to its size, shape, thickness or function. Thecards described herein could for example be a plastic card such as abanking card, or ID card. It will also be understood that each exampledescribed herein could be implemented within a device adopting adifferent form factor that is not a card, for example a fob, a dongle ora security token (e.g. a USB token). Alternatively, the devicesdescribed herein could be integrated into a communication device such asa mobile phone or smartphone; a wearable device, such as a bracelet,watch, a glove/pair of gloves, a pin (e.g. a brooch), a badge or someother contactless wearable device.

Some cards described herein have been referred to as contactless cards.It will be understood that a contactless card, as described herein,refers to a card that can communicate with a reader through acontactless interface. However, each card described as a contactlesscard may also be capable of communication with a terminal through directphysical contact. Thus, the term ‘contactless’ has not been used hereinto exclude the possibility of contact functionality.

In the examples given above the term power may be understood to refer toany relevant feature of energy availability. Examples include availableenergy, voltage, so current and power or any combination thereof.

The applicant hereby discloses in isolation each individual featuredescribed herein and any combination of two or more such features, tothe extent that such features or combinations are capable of beingcarried out based on the present specification as a whole in the lightof the common general knowledge of a person skilled in the art,irrespective of whether such features or combinations of features solveany problems disclosed herein, and without limitation to the scope ofthe claims. The applicant indicates that aspects of the presentinvention may consist of any such individual feature or combination offeatures. In view of the foregoing description it will be evident to aperson skilled in the art that various modifications may be made withinthe scope of the invention.

1. A device for contactless communication with a terminal, the devicecomprising: an antenna for receiving a wireless signal emitted by theterminal; an embedded chip configured to generate data for communicationto the terminal to perform a first function associated with the device;and a module separate from the chip configured to perform processes aspart of a second function associated with the device, the module beingconnected to the antenna and comprising a power-harvesting unitconfigured to harvest power from the received wireless signal to powerat least the module.
 2. A device as claimed in claim 1, wherein the chipis connected to the antenna and comprises a power-harvesting unitconfigured to harvest power from the received wireless signal to powerthe chip.
 3. A device as claimed in claim 2, wherein the module isconfigured to harvest power from the received wireless signalindependently of the chip.
 4. A device as claimed in claim 2, whereinthe device is configured so that only the chip is arranged to managetransmission and reception of messages with the terminal.
 5. A device asclaimed in claim 2, wherein the device is configured so that only thechip is adapted to communicate messages with the terminal via theantenna.
 6. A device as claimed in claim 1, wherein the device is forcontact and contactless communication with the terminal, and furthercomprises: one or more contact elements connected to the embedded chipand the module and arranged to supply power to the embedded chip and themodule from the terminal when the device is in contact communicationwith the terminal.
 7. A device as claimed in claim 6, wherein the moduleis a biometric sensor module and the second function is biometricsensing of a user feature, the biometric sensor module comprising apower conditioning circuit coupled to the one or more contact elements;the power-harvesting unit and at least one other internal component ofthe module; the power conditioning circuit comprising: a circuit pathcoupled at a first end to the one or more contact elements and at asecond end to the power harvest unit and said at least one internalcomponent of the module; a switching element interconnecting a firstpart of the circuit path comprising the first end and a second part ofthe circuit path comprising the second end; a bypass circuit providing apath that bypasses the switching element, the bypass circuit permittingcurrent to flow in a direction from the first end to the second end ofthe circuit; and a coupling unit coupled to the first part of thecircuit path and the switching element; the circuit being arranged sothat: when the card is in contact communication with the terminal, powersupplied through the contact elements drives the switching element viathe coupling unit to an open configuration thereby limiting current toflow from the first end to the second end of the circuit through thebypass circuit; and when the card is in contactless communication withthe terminal, power harvested by the power-harvesting unit causes theswitching element to adopt an open configuration thereby preventingcurrent flow from the second end of the circuit to the first end of thecircuit.
 8. A device as claimed in claim 7, wherein the bypass circuitcomprises a diode that limits current flow to the direction from thefirst part of the circuit to the second part of the circuit.
 9. A deviceas claimed in claim 7, wherein the power-conditioning circuit containsonly a single switching element.
 10. A device as claimed in claim 7,wherein the switching element is a bi-polar transistor.
 11. A device asclaimed in claim 10, wherein the bi-polar transistor is aPNP-transistor, with the emitter of the transistor being electricallyconnected to the first part of the circuit path, and the collector beingelectrically connected to the second part of the circuit path.
 12. Adevice as claimed in claim 7, wherein the power conditioning circuitfurther comprises a low-pass filter, the bypass circuit forming part ofthe low-pass filter thereby limiting current to flow from the first endto the second end of the circuit through the low-pass filter when thecard is in contact communication with the terminal and the switchingelement is in an open configuration.
 13. A device as claimed in claim 1,wherein the module further comprises noise mitigation circuitryconfigured to use power harvested from the received wireless signal asthe device is brought into range of the terminal to store charge, and tosupply current demanded from one or more components of the module toinhibit current being drawn from the antenna during operation of thosecomponents.
 14. A device as claimed in claim 13, wherein the noisemitigation circuitry is located within the power harvesting unit.
 15. Adevice as claimed in claim 13, wherein the noise mitigation circuitrycomprises one or more charging elements for storing charge, the chargingelements being arranged to discharge to supply demanded current.
 16. Adevice as claimed in claim 15, wherein the noise mitigation circuitrycomprises: a rectifier circuit coupled to the antenna and configured tooutput a rectified voltage to charge a first charging element; andsupply regulation circuitry configured to output a regulated voltage tocharge a second charging element.
 17. A device as claimed in claim 15,wherein the noise mitigation circuit further comprises a control blockconfigured to control the amount of current supplied to the one or morecomponents from the charging elements in dependence on deviations ofdemanded current from those components.
 18. A device as claimed in claim16, wherein the supply regulation circuitry comprises a first voltageregulator coupled to the rectifier circuit and a first component of themodule, and a second voltage regulator coupled to the rectifier circuitand a second component of the module, the first voltage regulator beingconfigured to output a different regulated voltage level than the secondvoltage regulator.
 19. A device as claimed in claim 18, wherein thefirst component of the module is an ASIC configured to control a sensorforming part of the module, and the second component of the module is amicrocontroller unit, and wherein the first voltage regulator isconfigured to output a higher regulated voltage than the second voltageregulator.
 20. A device as claimed in claim 18, wherein the firstvoltage regulator is a low-dropout regulator, and the second voltageregulator is a switch-mode-power supply.
 21. A device as claimed inclaim 13, wherein the noise mitigation circuitry is located locally at acomponent of the module.
 22. A device as claimed in claim 1, wherein thechip is a secure element.
 23. A device as claimed in claim 1, whereinthe device is configured to communicate with the terminal in accordancewith the ISO14443 standard and/or the ISO7816 standard.
 24. A device asclaimed in claim 1, wherein the first function is one of: IDverification; physical access control; a financial transaction; personalinformation retrieval; health record retrieval.
 25. A device as claimedin claim 1, wherein the module is a biometric sensor module and thesecond function is a biometric authentication or enrolment of a user.26. A device as claimed in claim 1, wherein the device is a contactlesscard and the terminal is a point of sale terminal.